The present invention relates to liquid filters, particularly for water irrigation systems, however also useful for other industrial or domestic applications.
More specifically, the invention concerns filter devices of the type disclosed in our U.S. Pat. No. 6,398,037 issued Jun. 4, 2002 which is hereby incorporated by reference (hereinafter called “the Patent”).
The Patent relates to filter devices utilizing a battery of filter discs with reverse flushing water flow cycles wherein the discs were caused to spin under the impact of water jets impinging thereon (hereinafter referred to as “Spin-Clean Filters”).
For better understanding of the invention herein disclosed, reference shall be made to FIG. 1 which depicts the reverse flow spin-cleaning stage of the filter device (conforming FIG. 10 of the Patent except that the spin-cleaning stage is provoked by the reverse flow proper rather than by an external pressure command, a feature which is understood to be encompassed within the scope of the Patent).
Using the same reference numerals as in the Patent, the water (or other liquid) admitted through the outlet port 20 flows into the conduit 30a (and conduits 30b and 30c that are not shown) and, through an opening 102a (not existing in the Patent exemplified embodiment) into the cylinder space 40 of the cylinder-and-piston assembly 28. Under a pressure sufficient to overcome the force of the spring 52, the piston 58 along with the cap member 60 will slide towards the distal end of the filter 10, relieving the clamping of the filter discs battery 70. The stroke of piston 58 is delimited by a protrusion 104 formed at the housing member 12 (shown but not referenced in the Patent drawings). As will be explained later on, this need for an extra, exterior element for stopping the progress of the piston has been found disadvantageous and hence remedied by one aspect of the present invention.
Turning now to the proximal end of the filter device 10, there has been used a female screw-threaded ring portion 38 of the fixed member against which the filter discs are pressed for mounting the integral main filter core member 24 to the filter housing structure 14 intermediate female screw-threaded ring 82. This mounting or coupling arrangement has also been found worthy of improvement as will be explained in detail below.